3-Acetylindole (For preparation see synthetic page no.726)
4-(Dimethylamino) pyridine (Sigma Aldrich), ReagentPlus, ≥99%, 107700
p-Toluenesulfonyl chloride (Sigma Aldrich), reagent grade, ≥98%, T35955
N,N-Diisopropylethylamine (Sigma Aldrich), ≥99%, 550043
Hydrochloric acid (SD Fine Chemicals Ltd)
Dichloromethane (SD Fine Chemicals Ltd), directly used without drying

To the solution of 3-acetyl indole (100 mg, 1 mmol) in dichloromethane (5 ml) was added DMAP (4 mg, 0.05 mmol), p-toluenesulfonyl choride (131 mg, 1.1 mmol)) and N,N-diisopropylethylamine (164 µl, 1.5 mmol). The mixture was stirred at room temperature for 20 h. Reaction was then quenched by the addition of 10% hydrochloric acid (HCl). The reaction mixture was extracted with dichloromethane (50 ml X 3), and combined organic layer was evaporated on rotary evaporator. Purification by silica gel column chromatography (mesh 100-200) using EtOAc-hexane (2: 98 to 10: 90) as mobile phase gave 1-(1-tosyl-1H-indol-3-yl)ethanone as white solid (167 mg, 85% yield). It was confirmed by comparison of NMR data with literature values. (Che, Z.; Zhang, S.; Shao, Y.; Fan, L.; Xu, H.; Yu, X.; Zhi, X.; Yao, X.; Zhang, R. J. Agric. Food Chem. 2013, 61, 5696-5705. http://dx.doi.org/10.1021/jf400536q)

• p-Toluenesulfonyl choride and N,N-diisopropylethylamine have pungent smell and therefore should be handled cautiously.
• It is an exothermic reaction and therefore base should be added drop-wise.

1-(1-Tosyl-1H-indol-3-yl)ethanone: White solid, m. p. 155-157 °C;
¹H NMR (CDCl₃, 400 MHz): δ 8.30 (s, 1H), 8.20 (s, 1H), 7.93 (t, 1H, J = 6.8 Hz), 7.84 (d, 2H, J = 8.0 Hz), 7.39-7.27 (m, 4H), 2.58 (s, 3H), 2.38 (s, 3H);
HRMS: m/z 314.0827 calcd for C₁₇H₁₅NO₃S + H⁺ (314.0845);
IR (CHCl₃): 3401, 3126, 2924, 1658, 1596, 1540, 1477, 1445, 1385, 1373, 1303, 1193, 1185, 1169, 1142, 1111, 1089, 1048, 1018 cm^-1.

Bharate, S. B.; Yadav, R. R.; Khan, S. I.; Tekwani, B. L.; Jacob, M. R.; Khan, I. A.; Vishwakarma, R. A. Meridianin G and its analogs as antimalarial agents. Med. Chem. Commun. 2013, 4, 1042-1048. http://dx.doi.org/10.1039/c3md00097d

MacKay, J. A.; Bishop, R. L.; Rawal, V. H. Org. Lett., 2005, 7, 3421-3424. http://dx.doi.org/10.1021/ol051043t